WASHINGTON (AP) — Charging that American students are getting a "third-world education" under President Barack Obama, Republican presidential challenger Mitt Romney on Wednesday proposed a voucher-style system that could significantly alter the public school system and revive the debate over school choice.

Romney, who has been reluctant to stray far from the economic issues at the core of the presidential campaign, outlined the proposal during a speech Wednesday at the U.S. Chamber of Commerce.

"Millions of kids are getting a third-world education. And America's minority children suffer the most," Romney declared. "This is the civil-rights issue of our era. And it's the great challenge of our time."

He continued: "President Obama has made his choice, and I have made mine. As president, I will be a champion of real education reform in America."

Romney said he would let low-income and disabled students use federal money to attend public schools, public charter schools and, in some cases, private schools. Federal funds could also be used for tutoring or digital courses.

The plan is line with GOP reforms aimed at giving students more educational choices. But it's unclear how schools in areas that depend on the federal funding would fare.

The proposal was not expected to include any new federal money for education.

Romney so far has offered few details for his plans on several key policy areas, including foreign policy, health care and education. He attacked Obama's education policy and said it's heavily influenced by campaign contributions from teachers' unions.

"The teachers' unions are the clearest example of a group that has lost its way," Romney said. "The teachers unions don't fight for our children."

The message is consistent for Romney, who regularly heaps criticism on the Democratic president's policies but until now has only offered a vague road map for what he would do as president.

White House spokesman Jay Carney said Wednesday that Romney's shift to education was welcome after a campaign season in which he said the GOP rarely mentioned the issue.

"Education never came up in the Republican primary in any of the debates, or if it did, it came up almost never," Carney said.

Carney said Obama's education initiatives have received broad bipartisan support and that the president "looks forward to defending that record."

Taking a sharper tact, Obama's campaign said the budget Romney signed into law as Massachusetts governor cost 14,500 teachers, librarians and school police officers their jobs.

"Not exactly the record of a job creator," campaign spokesman Ben LaBolt said.

"Mitt Romney gave a vague, detail-free speech this morning on education and confirmed, as if there were any doubt, just how far back he would take us," LaBolt told reporters on a conference call arranged to respond to Romney's speech.

Romney's shift carries some risk. His regular criticism of labor unions, in particular, threatens to alienate voters in Rust Belt states like Michigan, Ohio and Pennsylvania, where a close election may be decided.

Before the speech, Romney announced Tuesday a team of education policy advisers that includes former Education Secretary Rod Paige and other officials from President George W. Bush's administration. Paige is among several prominent opponents of teachers' unions on the panel. As education secretary in 2004, he labeled the National Education Association a "terrorist organization."

Romney's positions on education have evolved over time. He once supported abolishing the Education Department but reversed that position as a presidential candidate in 2007. At the time, he said he came to see the value of the federal government in "holding down the interests of the teachers' unions" and putting kids and parents first.

Romney also changed his position on the Bush-era education overhaul known as "No Child Left Behind." He said he supported the law as a candidate in 2007, but he has since generally come out against the policy many conservatives see as an expansion of the federal government.

Romney continues to support the federal accountability standards in the law, however. He also has said the student testing, charter-school incentives and teacher evaluation standards in Obama's "Race to the Top" competition "make sense," although the federal government should have less control over education. The campaign in recent days has emphasized his support for charter schools while governor of Massachusetts, a theme Romney weaved into Wednesday's address and met with opposition from Obama's team.

"We know from experience that private school vouchers have failed to raise achievement and they drain resources from public schools that serve the vast majority of children," Obama policy director James Kvaal said on the conference call.

The speech represents Romney's first public event in four days. Working to close Obama's cash advantage, he's coming off a three-day fundraising swing in the New York area that his chief finance aide said had netted $15 million. A single finance event in Manhattan on Tuesday evening generated $5 million.

Still, the campaign is eager to drive a positive message for voters now tuning in to the contest.

The education speech follows a relatively quiet phase for Romney, who has been focused on fundraising but usually delivers one major address a week. Most of his recent speeches, however, have been about the economic themes that so far have defined his campaign.